Meiosis, Mitosis, and Genetic Mutations Overview

Somatic Cells

Diploid cells located in various parts of the body including nerve cells, blood cells, and adipose cells.

Gametic Cells

Haploid cells usually referred to as reproductive cells, located in the ovaries and testes.

Chromosome pairs 1-22

Autosomes that relate back to somatic cells.

Chromosome pair 23

Gametic chromosome pair that ties into sex chromosomes, X and Y, determining gender in mammals.

Mitosis

A process that produces genetically identical cells, results in diploid cells, takes place throughout an organism's lifetime, and is involved in asexual reproduction.

Meiosis

A process that produces genetically unique cells and results in haploid cells.

Crossing Over

The exchange of chromosome segments between homologous chromosomes that occurs during prophase 1 of meiosis 1.

Genetic Linkage

The tendency of genes located close together on a chromosome to be inherited together.

Mutations

Changes or damages to a DNA gene that alter the genetic message, occurring in somatic cells or gametes.

Effects of Mutations

Some mutations have little or no effect, some produce beneficial variations, and some negatively disrupt gene function.

Source of Genetic Variability

Mutations are the source of genetic variability in a species, allowing for evolution.

Causes of Mutations

Mutations can be caused by chemicals and UV radicals.

Repair of Mutations

Many mutations can be repaired by enzymes.

46 chromosomes

The total number of chromosomes in each diploid cell.

Haploid Cells

Cells that contain half the number of chromosomes, specifically one set of chromosomes.

Diploid Cells

Cells that contain two sets of chromosomes, one from each parent.

Asexual Reproduction

A type of reproduction that involves only one parent and produces genetically identical offspring.

Sexual Reproduction

A type of reproduction that creates unique combinations of genes through the process of meiosis.

Prophase 1 of Meiosis 1

The stage in meiosis where crossing over occurs.

Chromosomes

Structures that contain many genes, which can be separated during crossing over.

Genetic Linkage Maps

Maps that show the likelihood of genes being separated by crossing over based on their distance on a chromosome.

Chromosome Segments

Parts of chromosomes that can be exchanged during crossing over.

Neutral mutations

No effect on organism's survival; increase genetic diversity in a species (Example: eye color)

Harmful mutations

Decrease organism's survival; produce genetic disorders or unfavorable traits (Example: cancers)

Helpful mutations

Increase organism's survival; produce favorable traits (Example: antibiotic resistance in bacteria)

Chromosome mutations

Changing the structure of a chromosome or the loss or gain of part of a chromosome

Deletion

Involves the loss of all or part of a chromosome

Inversion

Reverses the direction of parts of a chromosome

Translocation

Occurs when part of one chromosome breaks off and attaches to another

Nondisjunction

Failure of chromosomes to separate properly during cell division

Duplication

Produces an extra copy of all or part of a chromosome

Gene mutations

Change in the nucleotide sequence of a gene

Point mutations

Mutations that involve a change in a single nucleotide

Substitutions

In a substitution, one base is changed to a different base (Example: adenine replaced by guanine)

Insertions

Point mutations where one base is inserted into the DNA sequence

Deletions

Point mutations where one base is removed from the DNA sequence

Frameshift mutations

Mutations that shift the reading frame of the genetic message, potentially altering every amino acid that follows

Gregor Mendel

Commonly referred to as the 'Father of Genetics' and laid the groundwork for most of our knowledge on genetics today

Mendel's experiments

Involved using only purebred plants, controlled breeding, and observing either/or traits

Dominant

In genetics, describes an allele that is fully expressed whenever this allele is present in an individual

Recessive

In genetics, describes an allele that is expressed only when no dominant allele is present in an individual

Segregation

When meiosis makes sex cells, each cell has one allele from mom and one from dad; no allele is favored or has an advantage over another

Independent assortment

Each trait is passed on independently of other traits

Heterozygous

Describes an individual that carries two different alleles of a gene

Genome

The complete genetic material contained in an individual or species

Genotype

The entire genetic makeup of an organism; also the combination of genes for one or more specific traits

Phenotype

An organism's appearance or other detectable characteristic that results from the organism's genotype and the environment

Punnet Square

A graphic used to predict the results of a genetic cross

Monohybrid Cross

A cross between individuals that involves one pair of contrasting traits

Testcross

A cross between an organism with an unknown genotype and an organism with a recessive phenotype

Dihybrid Cross

A cross between individuals that have different alleles for the same gene